Monday, June 3, 2013

Solve for x the equation 2^2x=6^(x+1) - 5*3^2x?

We'll move all terms to the left
side:


2^2x - 6^(x+1) + 5*3^2x =
0


We'll write 6^x = 2^x*3^x, also 6^(x+1) =
(6^x)*6


6^(x+1) =
6*2^x*3^x


We'll re-write the
equation:


2^2x - 6*2^x*3^x + 5*3^2x =
0


We'll divide by
3^2x:


(2/3)^2x - 6*(2/3)^x + 5 =
0


We'll substitute (2/3)^x =
t


t^2 - 6t + 5 = 0


We'll apply
quadratic formula:


t1 = [6 +
sqrt(36-20)]/2


t1 = (6+4)/2


t1
= 5


t2 = (6-4)/2


t2 =
1


We'll substitute (2/3)^x = 1, where 1 =
(2/3)^0


(2/3)^x = (2/3)^0 <=> x =
0


(2/3)^x = 5 <=> x*ln (2/3) = ln
5


x = ln
5/ln(2/3)


The values of x that represent the
solutions of the equation are: x = 0 and x = (ln
5)/ln(2/3).

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